Heavy duty motor vehicle cab suspension

ABSTRACT

An apparatus for supporting a cab of a conventional over-the-highway truck or tractor vehicle relative to a vehicle frame which includes a pair of longitudinally extending rails and a transverse member interconnecting the rails. A pair of mounting assemblies are located near the front of the cab to resiliently and pivotally connect the cab to the rails. A pair of spaced apart spring members are located near the rear of the cab to support the cab for limited movement relative to the frame. A spaced pair of dampers extends between the cab and the frame to damp movement of the cab. The spaced dampers are located between the spring members. A centering damper is mounted between the cab and the frame to damp transverse movement of the cab. The centering damper is located between the spaced dampers.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to an over-the-highway truck ortractor vehicle having a frame and a cab. In particular, the presentinvention relates to a system for suspending the cab relative to theframe and for damping relative movement between them.

2. Description of the Prior Art

A conventional over-the-highway truck or tractor vehicle includes aframe for supporting an operator's cab. The frame is typically supportedby load springs extending between the frame and the axles of thevehicle. Due to the relatively large load that such a vehicletransports, the load springs have a relatively high spring rate. Thus,any uneven road surface that the vehicle is operating over or anyimbalance or untrueness of the tire and wheel assemblies of the vehicleresults in a shock or vibration that is transmitted to the operator'scab.

Cab suspensions have been developed which include cab springs anddampers located between the vehicle frame and operator's cab to minimizetransmission of such shock and vibration to the cab. Some developmentsin cab suspensions locate at least part of the suspension system nearthe rear of the cab and close to the center of gravity of the vehicle.

SUMMARY OF THE INVENTION

The present invention is directed to a cab suspension system withsuspension components located as closely as possible to the corners ofthe cab to maximize the control of movement of the cab relative to thevehicle frame. An apparatus of the present invention provides a systemfor supporting a cab of a conventional over-the-highway truck or tractorvehicle on a vehicle frame. The frame includes a pair of longitudinallyextending rails and transverse members interconnecting the rails.

The apparatus includes a pair of mounting assemblies located near thefront end of the cab. Each mounting assembly resiliently and pivotallyconnects a portion of the front end to a respective one of the rails.Each of the mounting assemblies includes a cab bracket portion and aframe bracket portion with an interposed elastomeric bushing. A shaftinterconnects the cab bracket portion to the elastomeric bushing of theframe bracket portion. The elastomeric bushings and shafts extendlongitudinally of the vehicle so that the bushings permit limitedpivotal movement of the cab about a transverse axis.

A spaced pair of spring members is located near the rear end of the cab.Each spring member extends between the cab and the frame to support therear end of the cab for limited pivotal movement relative to the frame.A spaced pair of first upright dampers extends between the cab and theframe to damp vertical movement of the rear end of the cab. The uprightdampers are located between the spring members. A centering damper ismounted between the cab and the frame to damp transverse movement of thecab. The centering damper is located between the upright dampers.

Each of the spring members is connected to a respective end of atransverse member at a location outboard of the rails. Preferably, eachof the spring members extends in a direction substantially normal to therails. In one embodiment, each of the spring members is a fluid springand a mechanism is provided to actively control the pressure in thespring members. In another embodiment, each spring member is a coilspring.

A lower end of each of the upright dampers is connected to thetransverse member at a location above a respective frame rail. Eachupright damper has an upper end connected to the cab at a locationtransversely outward of a lower damper end. The centering damperincludes a housing and a pair of springs, each of which acts on anopposite side of the housing to bias the cab to a laterally centeredposition relative to the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a portion of a conventionalover-the-highway tractor having a cab suspension system embodying thepresent invention;

FIG. 2 is a fragmentary rear elevational view on an enlarged scale ofthe cab and suspension system of FIG. 1, as seen from the planeindicated by the line 2--2 in FIG. 1;

FIG. 3 is a view similar to FIG. 2 illustrating an alternate embodimentof the cab suspension system;

FIG. 4 is an enlarged view, partly in section, of a cab mountingassembly; and

FIG. 5 is an enlarged cross-sectional view of a centering damper.

DESCRIPTION OF PREFERRED EMBODIMENT

A suspension system 20 for use on a conventional over-the-highway truckor tractor vehicle 22 is illustrated in FIG. 1. The vehicle 22 includesa frame 24 to support an operator's cab 26. The frame 24 includes a pairof longitudinal, or fore and aft, extending rails 42 and a transversemember 44 (FIG. 2) is positioned on and interconnects the rails. Thetransverse member 44 extends laterally beyond the rails 42 such that thelength of the transverse member corresponds to approximately the widthof the cab 26. The transverse member 44 is located under a rearwardportion of the cab 26.

The suspension system 20 supports the cab 26 for limited movementrelative to the frame 24. The suspension system 20 also damps movementof the cab 26 relative to the frame 24. The suspension system 20includes a spaced, mirror image, pair of mounting assemblies 62 locatedunder a forward portion of the cab 26, as illustrated in FIG. 1. Thesystem 20 also includes a spring/damper system 64 located under arearward portion of the cab.

The mounting assemblies 62 resiliently and pivotably connect respectivesides of the forward portion of the cab 26 to the rails 42. Eachmounting assembly 62 (FIG. 4) includes a cab bracket portion 82 which isfixed to the cab 26 in a suitable manner, such as by welds. A framebracket portion 84 of the mounting assembly 62 is connected to the rail42 of the frame 24 by suitable means, such as threaded fasteners. Theframe bracket portion 84 includes an upper end portion 86, as viewed inFIG. 4, with a bore 87 which receives an elastomeric bushing 88.

A bolt 102 having a shaft 104 extends coaxially through the bushing 88and the bore 87 to interconnect the cab bracket portion 82 with theframe bracket portion 84. The bushing 88 and the shaft 104 extendlongitudinally of the vehicle 22 in a direction substantially parallelto the rails 42. Thus, each of the mounting assemblies 62 permits alimited amount of pivoting action of the cab 26 relative to the frame 24about a transverse axis. Each mounting assembly 62 also permits alimited amount of rolling and transverse movement of the cab 26 relativeto the frame 24 in a direction transverse to the rails 42.

Two alternate embodiments of the spring/damper portion 64, 142 of thesuspension system 24 are illustrated in FIGS. 2 and 3. While thestructures are different, the function of the two embodiments of thespring/damper portion 64, 142, is the same. The embodiment, illustratedin FIG. 2, of the spring/damper portion 64 includes a pair of airsprings 122 and a pair of vertical travel limits 124 in the form ofelastomeric bumpers. Pressure within each of the air springs 122 ismonitored and established by a controller 126. The controller 126monitors the relative position or distance D between the cab 26 and theframe 24, and controls fluid pressure in the air springs 122 as afunction of the relative distance between the cab and the transversemember 44. The embodiment illustrated in FIG. 3 of the spring/damperportion 142 includes a pair of coil springs 144 and vertical travellimits 146 respectively extending coaxially within the springs.

Each pair of springs 122, 144 is spaced apart transversely along thetransverse member 44. Each of the springs 122, 144 is located betweenthe transverse member 44 and a respective longitudinally extendingsupport 128 on the bottom or underfloor of the cab 26. Each spring 122,144 is located substantially as far as possible outboard on respectiveelements in the form of cantilevered outboard end portions 148 of thetransverse member 44. Thus, the springs 122, 144 are located as close tocorners at the rear of the cab 26 as is feasible. With the describedpositioning springs 122, 144 of relatively light weight and relativelylower spring rates can be used to offer maximized control of theposition and movement of the cab 26 relative to the frame 24.

A transversely extending cab frame member 160 is located under the cab26. A pair of laterally spaced apart upright dampers 162 are connectedbetween the transverse member 44 and cab frame member 160. The uprightdampers 162 damp and control primarily vertical movement of the cab 26relative to the frame 24. The upright dampers 162 are shock absorberswhich are located between the springs 122, 144 as upright dampers 162 islocated as close as is feasible to an associated spring to maximizedamping at each rearward corner of the cab 26.

A lower end 164 of each upright damper 162 is connected to thetransverse member 44 above a respective rail 42 at a locationsubstantially within the lateral extent E of the rail. An upper end 166of each upright damper 162 is located transversely or laterally outwardof the location of the bottom end portion 164 outside of the lateralextent E of the rails 42. Such a canted orientation of the uprightdampers 162 modulates a portion of rolling and/or transverse movement ofthe cab 26 relative to the frame 24.

A lateral or centering damper 182 is located between the upright dampers162. The lateral damper 182 controls a relatively large amount ofrolling and/or transverse movement of the cab 26 relative to the frame24 by damping and biasing the cab to a neutral or centered positionrelative to the frame. A lower or right end 184 (FIGS. 2 and 5) of thecentering damper 182 is fixed to a bracket 186 connected to thetransverse member 44. An upper or left end 188 of the centering damper182 is pivotally connected to a bracket 200 fixed to the cab framemember 160.

The centering damper 182 includes an annular end cap 204 fixed to acylindrical housing 206. Coil springs 208, 210 are located on eitherside of the end cap 204. The spring 208 is located coaxially around adamper rod 222 that extends from the upper end 188 through the end cap204. The rod 222 is connected to a damper piston 224 which reciprocateswithin and relative to the housing 206 to damp movement equally ineither direction the rod 222.

A tubular cover 226 extends from the end 188 to a remote portion whichis telescoped over and reciprocatable relative to the housing 206. Thespring 208 is interposed between and engages the cover 226 and the endcap 204. The spring 210 is located coaxially about the rod 222 and isinterposed between and engages the end cap 204 and the piston 224.

The spring rate of the springs 208, 210 are equal and act on oppositesides of the end cap 204. The centering damper 182 biases the cab 26 toa transversely neutral or centered position relative to the frame rails42. The lateral damper 182 also serves as a fluid damper or shockabsorber to damp rolling and/or lateral movements of the cab 26 relativeto the rails 42.

From the above description of preferred embodiments of the invention,those skilled in the art will perceive improvements, changes andmodifications. Such improvements, changes and modifications within theskill of the art are intended to be covered by the appended claims.

Having described at least one preferred embodiment of the invention,what is claimed is:
 1. In a conventional over-the-highway truck ortractor having a frame including at least two fore and aft extendingrails and a transverse member interconnecting the rails and a cabmounted on the frame behind an engine, an improved cab suspension forenhancing ride quality comprising:a spaced pair of mounting assembliesconnecting a forward portion of the cab to the frame rail for limitedpivotal movement about an axis transverse of the rails; a pair of spacedapart springs interposed between and connected to a rearward portion ofthe cab and to the transverse member outboard of the rails formodulating pivotal motion of the cab relative to the frame and about theaxis; a pair of spaced apart motion dampers interposed between anddirectly connected to the cab and to the transverse member at locationsbetween the pair of springs; the motion dampers being oppositely cantedat acute angles relative to the frame;the motion dampers interconnectingthe cab and frame to damp and limit relative cab and frame movement bothtoward and away from one another; and, a centering damper interposedbetween and connected to the cab and directly to the frame transversemember, the centering damper being between the motion dampers andadapted to bias the cab toward a transversely centered position relativeto the frame rails.
 2. The apparatus in claim 1 wherein each of saidspring members extends in a direction substantially normal to the rails.3. The apparatus in claim 1 wherein each of said spring members is afluid spring and further includes a mechanism for actively controllingthe pressure in the spring members.
 4. The cab suspension of claim 1wherein said centering damper includes a housing and a pair of springsacting on opposite sides of said housing to bias the cab to atransversely centered position relative to the frame.
 5. The cabsuspension of claim 1 wherein the springs are air springs.
 6. The cabsuspension of claim 1 wherein the springs are coil springs.